1. Field of the Invention
The present invention concerns a color sheet of a sublimating type and a color transfer method using such a sheet and, more particularly, relates to a color sheet of a sublimating type in which a degree of clearness of the printing is improved and a required time for printing is shortened and a color transfer method using the same.
2. Description of the Related Art
Generally, there is known a sublimation thermal transfer method as one of printing methods capable of making excellent gradations which is frequently used in a full color printer of a thermo-sensitive type or a video printer. As shown in FIG. 1, the sublimation thermal transfer method above method is based on the following principle. That is, a color sheet 100 is prepared which comprising a heat resistant lubricating layer 101 on one side of the substrate 102 and a dye layer 103 is coated on the other side of the substrate. The dye layer 103 contains a sublimating solid ink of yellow, cyan or magenta which is solid at room temperature. The dye layer 103 is heated and sublimated by a thermal head 105 contacted with the lubricating layer 101. The sublimated dye is diffused and fixed into a receptor layer 121 on an image receiving base plate 120 of a paper contacting with the dye layer, thereby forming an image on the paper.
In the conventional method utilizing the thermal head, there are problems of the facts that not only a sublimation point of the dye is so high to lie within a range from 130.degree. to 200.degree. C., but also a thermal speed of response of the thermal head 105 is low. In order to heat and sublimate the dye in the dye layer 103 through both the lubricating layer 101 and the substrate 102 and to transfer the sublimated dye to the receptor layer 121, there are consequently problems such that the thermal head must be slowly moved with respect to the thermal transfer medium of the paper while applying a fairly large amount of heat energy to the latter, so that a recording speed becomes extremely slow.
Furthermore, in the case of using the conventional thermal head method, the periphery of one fine dot is influenced by the heat diffusion and then a blur of the formed image occurs. There is inherently a limitation to obtain a clear image as a result, i.e., the resolution doesn't exceed a certain limit value, even if a thermal head having very small heat generating elements will be manufactured in order to form the very fine recording dots.